In the Eudoridoidea the gills can be withdrawn into a pocket for protection. Another name for the superfamily is the "Cryptobranchia" which basically means "hidden gills".

Most characteristic is the way the gills are held, a small clump held closed with all the tips pointed inwards and almost touching, forming a globe

Two genera are included in this family : Actinocyclus and Hallaxa

Hallaxa with small species and Actinocyclus with very large species

Photo : Actinocyclus verrucosus

Characteristics :

The body is very humped and domed in Actinocyclus, firm to the touch in both, often with low rounded pustules and hollows or pits to resemble sponge osculae

Feeding behavior :

Actinocyclus feeds on non spiculose sponges

Photo : Actinocyclus verrucosus

Characteristics :

The buccal tentacles are described as "lobiform", which are characteristic of Hallaxa

Feeding behavior :

Hallaxa feeds on siliceous sponges

Photo : Hallaxa fuscescens